JP2016075836A - Pixel circuit, method for driving the pixel circuit, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pixel circuit capable of preventing reduction in contrast due to leakage light emission at a resetting operation.SOLUTION: A pixel circuit 10 includes: a light-emitting element 11; a driving transistor (M3) supplying a current for an applied voltage to the light-emitting element 11; a capacitor part 12 holding a voltage including a threshold voltage Vth and a data voltage Vdata of the driving transistor (M3) and applying the voltage to the driving transistor (M3); and a switch part 13 causing the capacitor part 12 to hold the voltage containing the threshold voltage Vth and the data voltage Vdata. The switch part 13 has a current bypass transistor (M6) causing a current supplied from the driving transistor (M3) to directly flow to a reference voltage power source line (P3) bypassing the light emitting element 11.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a pixel circuit used in an active matrix organic EL display (hereinafter referred to as “AMOLED: Active Matrix Organic Light Emitting Display”), a driving method thereof, and a display device including the pixel circuit. The organic light emitting diode is also referred to as an organic EL element, but is hereinafter referred to as “OLED (Organic Light Emitting Diode)”.

  Since there is no standard pixel circuit of AMOLED, each company that manufactures AMOLED uses its own pixel circuit. Hereinafter, a basic pixel circuit will be described. FIG. 9A is a circuit diagram showing a basic pixel circuit, FIG. 9B is a waveform diagram showing a driving method thereof, and FIG. 9C is a graph showing output characteristics of a driving TFT (Thin Film Transistor) included in the pixel circuit.

  The pixel circuit 900 includes a switch TFT 901, a driving TFT 902, a capacitor 903, and an OLED 904, and is driven and controlled by a two-transistor method. Both the switch TFT 901 and the drive TFT 902 are p-channel FETs (Field Effect Transistors). The gate terminal of the switch TFT 901 is connected to the scanning line 905, and the drain terminal of the switch TFT 901 is connected to the data line 906. The gate terminal of the driving TFT 902 is connected to the source terminal of the switch TFT 901, the source terminal of the driving TFT 902 is connected to the power supply line 907 (power supply voltage VDD), and the drain terminal of the driving TFT 902 is connected to the anode terminal of the OLED 904. A capacitor 903 is connected between the gate terminal and the source terminal of the driving TFT 902. A power supply line 908 (power supply voltage VSS) is connected to the cathode terminal of the OLED 904.

  In this configuration, when a selection pulse (scanning signal Scan) is output to the scanning line 905 and the switch TFT 901 is turned on, the data signal Vdata supplied via the data line 906 is written to the capacitor 903 as a voltage value. The holding voltage written in the capacitor 903 is held throughout one frame period, and the conductance of the driving TFT 902 changes in an analog manner by this holding voltage, and a forward bias current corresponding to the light emission gradation is supplied to the OLED 904.

  By driving the OLED 904 with a constant current in this way, the light emission luminance of the OLED 904 can be kept constant even if the resistance value changes due to the deterioration of the OLED 904.

  In this type of pixel circuit, a technique for detecting the threshold voltage is known in order to compensate for variations and fluctuations in the threshold voltage of the driving transistor that supplies current to the OLED (see, for example, Patent Documents 1 and 2). There are two main types of threshold voltage detection techniques as follows. (1) The gate terminal and the drain terminal are connected, the drive transistor is temporarily turned on, and a current flows between the drain terminal and the source terminal, whereby the gate-source voltage Vgs is automatically increased to the threshold voltage Vth. Technology (diode connection type). (2) A technique for automatically bringing the gate-source voltage Vgs close to the threshold voltage Vth by fixing the potential of the gate terminal, temporarily turning on the driving transistor, and passing a current between the drain terminal and the source terminal ( Source follower type). This source follower type has an advantage that the threshold voltage Vth can be detected even for a depletion type transistor in which a current flows even when Vgs = 0V.

US Patent Application Publication No. 2013/0169611 JP 2012-128386 A

  However, the existing pixel circuit having the threshold voltage detection function has the following problems.

  (1) Contrast reduction occurs due to leakage light emission during the reset operation. This is because, as described below, a current flows through the OLED during the non-light emission period, and invalid leakage light emission occurs. (a) During the threshold voltage detection period, a current flowing through the driving transistor flows through the OLED. (b) During the capacitor reset period, the capacitor charging current flows through the OLED.

  (2) Due to the hysteresis characteristics of the drive transistor, even if a black display is displayed for a while and then a white display is performed, it does not immediately become white, but finally becomes all white over several frames. This is generally called image retention. In other words, the hysteresis characteristic of the drive transistor is initialized unless a current is passed through the drive transistor for a long time, and even if a white display Vgs bias determined based on the initialized hysteresis characteristic is applied. When the light is turned on, the current is instantaneously reduced due to the hysteresis characteristic, so that the original brightness of white display is not obtained.

  (3) Since the threshold voltage detection period is limited to one horizontal scanning period, the compensation accuracy of the threshold voltage deteriorates as the definition increases.

  The threshold voltage is detected at a time when the reference voltage is supplied from the data line within one horizontal scanning period, or at a time when the data voltage is supplied from the data line within one horizontal scanning period (for example, FIG. 1 of FIG. 1). .4, see FIG. 4 of Patent Document 2). Therefore, if an attempt is made to detect the threshold voltage over one horizontal scanning period or more, crosstalk occurs due to the influence of the data voltage supplied to the adjacent pixel circuit.

  On the other hand, as the definition becomes higher, the number of scanning lines increases, thereby shortening one horizontal scanning period. When one horizontal scanning period is shortened, the threshold voltage detection period is also shortened. Therefore, the threshold voltage detection must be completed before the gate-source voltage Vgs reaches the threshold voltage Vth. As a result, the detection accuracy of the threshold voltage is lowered, and the compensation accuracy of the threshold voltage is also deteriorated.

  Therefore, the object of the present invention is to first prevent a decrease in contrast due to leakage light emission during a reset operation, secondly prevent image retention, and thirdly improve threshold voltage detection accuracy. The object is to provide a pixel circuit or the like to be realized.

A pixel circuit according to the present invention includes:
A light emitting element;
A drive transistor for supplying a current corresponding to the applied voltage to the light emitting element;
A capacitor unit that holds a voltage including a threshold voltage and a data voltage of the driving transistor and applies the voltage to the driving transistor;
A switch unit that holds the voltage including the threshold voltage and the data voltage in the capacitor unit;
In a pixel circuit comprising:
The switch unit includes a current bypass transistor that bypasses the current supplied from the drive transistor to a reference voltage power line without passing through the light emitting element.
It is characterized by that.

  According to the present invention, since the current bypass transistor for bypassing the current supplied from the drive transistor to the reference voltage power supply line without passing through the light emitting element is provided, the reset is performed by turning on the current bypass transistor during the reset operation. It is possible to prevent a decrease in contrast due to leakage light emission during operation.

2 is a circuit diagram illustrating a configuration of a pixel circuit according to Embodiment 1. FIG. FIG. 3 is a timing diagram illustrating an operation of the pixel circuit according to the first embodiment. 1 is a plan view showing a display device including a pixel circuit according to Embodiment 1. FIG. It is sectional drawing which expands and shows a part of FIG. FIG. 6 is a circuit diagram in a first period, illustrating an operation (a driving method) of the pixel circuit according to the first embodiment. FIG. 6 is a timing diagram in the first period, illustrating the operation (driving method) of the pixel circuit according to the first embodiment. FIG. 6 is a circuit diagram in a second period, illustrating the operation (driving method) of the pixel circuit of Embodiment 1. FIG. 6 is a timing diagram illustrating the operation (driving method) of the pixel circuit of Embodiment 1 in a second period. FIG. 6 is a circuit diagram in a third period, illustrating the operation (driving method) of the pixel circuit of Embodiment 1. FIG. 9 is a timing chart in the third period, illustrating the operation (driving method) of the pixel circuit according to the first embodiment. FIG. 6 is a circuit diagram in a fourth period illustrating an operation (driving method) of the pixel circuit according to the first embodiment. FIG. 9 is a timing diagram in the fourth period, illustrating the operation (driving method) of the pixel circuit according to the first embodiment. FIG. 6 is a circuit diagram illustrating a part of a display device according to a third embodiment. FIG. 10 is a timing diagram illustrating an operation of the display device according to the third exemplary embodiment. It is a circuit diagram which shows a basic pixel circuit. It is a wave form diagram which shows the drive method of a basic pixel circuit. It is a graph which shows the output characteristic of the drive TFT (Thin Film Transistor) contained in a basic pixel circuit.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. In the present specification and drawings, the same reference numerals are used for substantially the same components. The shapes depicted in the drawings are drawn so as to be easily understood by those skilled in the art, and thus do not necessarily match the actual dimensions and ratios. The term “comprising” in the present specification and claims includes a case of including elements other than the specified elements. The same applies to “having” and “including”. The term “connecting” in the present specification and claims includes not only the case where two elements are directly connected but also the case where two elements are connected via another element. “On” and “off” of a transistor can be referred to as “conducting” and “non-conducting”, respectively.

<Embodiment 1>
FIG. 1A is a circuit diagram illustrating a configuration of a pixel circuit according to the first embodiment, and FIG. 1B is a timing diagram illustrating an operation of the pixel circuit according to the first embodiment. Hereinafter, description will be given based on this drawing.

  The pixel circuit 10 of Embodiment 1 includes a light emitting element 11, a driving transistor (M3) that supplies a current corresponding to the applied voltage to the light emitting element 11, a threshold voltage Vth and a data voltage Vdata of the driving transistor (M3). And a switch unit 13 that holds the voltage including the threshold voltage Vth and the data voltage Vdata in the capacitor unit 12. The switch unit 13 includes a current bypass transistor (M6) that bypasses the current supplied from the drive transistor (M3) to the reference voltage power line (P3) without passing through the light emitting element 11.

  The switch unit 13 turns on the drive transistor (M3) and the current bypass transistor (M6) before the capacitor unit 12 holds the voltage including the threshold voltage Vth and the data voltage Vdata.

  Further, the switch unit 13 includes a reference voltage transistor (M5) for inputting the reference voltage (Vref) from the reference voltage power supply line (P3), and a data voltage transistor (M1) for inputting the data voltage Vdata from the data line D. Have

  More specifically, the driving transistor (M3) has a gate terminal, a source terminal, and a drain terminal, and a current corresponding to a voltage applied between the gate terminal and the source terminal is connected to the drain terminal. The light emitting element 11 is supplied. The capacitor unit 12 holds a voltage including the threshold voltage Vth and the data voltage Vdata, and applies this voltage between the gate terminal and the source terminal of the driving transistor (M3). The switch unit 13 includes a plurality of transistors including a current bypass transistor (M6), a reference voltage transistor (M5), and a data voltage transistor (M1). By the switching operation of these transistors, the capacitor unit 12 A voltage including the threshold voltage Vth is held, and then a voltage including the threshold voltage Vth and the data voltage Vdata is held. The switch unit 13 turns on the current bypass transistor (M6) and the reference voltage transistor (M5) and turns off the data voltage transistor (M1) when the capacitor unit 12 holds the voltage including the threshold voltage Vth. Thus, when supplying the reference voltage Vref to the capacitor unit 12 and holding the voltage including the threshold voltage Vth and the data voltage Vdata in the capacitor unit 12, the current bypass transistor (M6) and the reference voltage transistor (M5) ) Is turned off and the data voltage transistor (M1) is turned on, whereby the data voltage Vdata is supplied to the capacitor unit 12.

  The pixel circuit 10 according to the first embodiment includes the current bypass transistor (M6) that bypasses the current supplied from the drive transistor (M3) to the reference voltage power supply line (P3) without passing through the light emitting element 11. By turning on the current bypass transistor (M6) during the reset operation, it is possible to prevent a decrease in contrast due to leakage light emission during the reset operation.

  Further, according to the pixel circuit 10, before the voltage including the threshold voltage Vth and the data voltage Vdata is held in the capacitor unit 12, the drive transistor (M3) and the current bypass transistor (M6) are turned on to emit light. Since the current can be reliably passed through the drive transistor (M3) before supplying the current to the element 11, initialization of the hysteresis characteristic of the drive transistor (M3) can be prevented, and image retention can be prevented without causing a decrease in contrast. Can be prevented.

  Further, according to the pixel circuit 10, apart from the data voltage transistor (M1) that inputs the data voltage Vdata from the data line D, the reference voltage transistor that inputs the reference voltage (Vref) from the reference voltage power line (P3). By providing (M5), the threshold voltage Vth can be detected without using the reference voltage (Vref) supplied from the data line D. Therefore, in principle, no crosstalk occurs at the time of detecting the threshold voltage Vth, so that the threshold voltage detection period can be sufficiently set even when the definition is advanced, and the detection accuracy of the threshold voltage Vth can be improved.

  In addition, when the switch unit 13 holds the voltage including the threshold voltage Vth in the capacitor unit 12, the switch unit 13 turns on the current bypass transistor (M 6) and the reference voltage transistor (M 5) for a period of time equal to or longer than one horizontal scanning period. The reference voltage (Vref) may be supplied to the capacitor unit 12 by turning off the voltage transistor (M1). In this case, since the threshold voltage detection period can be set more sufficiently, the detection accuracy of the threshold voltage Vth can be further improved. The current bypass transistor (M6) and the reference voltage transistor (M5) may be turned on and the data voltage transistor (M1) may be turned off as long as possible within one horizontal scanning period.

  Furthermore, the switch unit 13 turns on the current bypass transistor (M6) and supplies the reference voltage (Vref) to the capacitor unit 12 when holding the voltage including the threshold voltage Vth in the capacitor unit 12. The driving transistor (M3) may be temporarily turned on. In this case, a minute current flowing through the drive transistor (M3) when the threshold voltage Vth is detected is caused to flow to the reference voltage power supply line (P3) without flowing through the light-emitting element 11 via the current bypass transistor (M6). Accordingly, it is possible to prevent a decrease in contrast due to leakage light emission.

  Next, the pixel circuit 10 will be described in more detail.

  The pixel circuit 10 is electrically connected to the data line D, the first to fourth control lines S1 to S4, and the first to third power supply lines P1 to P3, and includes first to sixth transistors M1 to M6, first to third. Second capacitors 21 and 22 and a light emitting element 11 are provided. The third power supply line P3 corresponds to the above-described reference voltage power supply line (P3), and the first, second, fourth, fifth and sixth transistors M1, M2, M4, M5, M6 serve as the above-described switch unit 13. The first transistor M1 corresponds to the data voltage transistor (M1), the fifth transistor M5 corresponds to the reference voltage transistor (M5), and the sixth transistor M6 is the current bypass transistor. The third transistor M3 corresponds to (M6), the drive transistor (M3), and the first and second capacitors 21 and 22 form the capacitor unit 12 described above.

  The first transistor M1 has a first terminal electrically connected to the data line D, a second terminal, and a control terminal electrically connected to the first control line S1. The second transistor M2 has a first terminal electrically connected to the first power supply line P1, a second terminal, and a control terminal electrically connected to the second control line S2.

  The third transistor M3 is electrically connected to the second terminal of the second transistor M2, and has a first terminal corresponding to the source terminal of the driving transistor (M3) and a drain terminal of the driving transistor (M3). And a control terminal that is electrically connected to the second terminal of the first transistor M1 and that corresponds to the gate terminal of the driving transistor (M3).

  The fourth transistor M4 has a first terminal electrically connected to the second terminal of the third transistor M3, a second terminal, and a control terminal electrically connected to the third control line S3.

  The fifth transistor M5 is electrically connected to the first terminal electrically connected to the third power supply line P3, the second terminal electrically connected to the second terminal of the first transistor M1, and the fourth control line S4. Connected control terminals.

  The sixth transistor M6 is electrically connected to the first terminal electrically connected to the third power supply line P3, the second terminal electrically connected to the second terminal of the third transistor M3, and the fourth control line S4. Connected control terminals.

  The first capacitor 21 has a first terminal electrically connected to the second terminal of the first transistor M1 and a second terminal electrically connected to the first terminal of the third transistor M3.

  The second capacitor 22 has a first terminal connected to the third power supply line P3 and a second terminal electrically connected to the first terminal of the third transistor M3.

  The light emitting element 11 has a first terminal electrically connected to the second terminal of the fourth transistor M4 and a second terminal electrically connected to the second power supply line P2.

  Here, the first control line S1 outputs the first control signal Scan, the second control line S2 outputs the second control signal EM, the third control line S3 outputs the third control signal BP, and the fourth The control line S4 outputs a fourth control signal Reset. In each transistor, the first terminal is, for example, one of a source terminal and a drain terminal, the second terminal is, for example, the other of the source terminal and the drain terminal, and the control terminal is, for example, a gate terminal. The first terminal of the light emitting element 11 is one of an anode terminal and a cathode terminal (for example, an anode terminal in the first embodiment), and the second terminal of the light emitting element 11 is the other of the anode terminal and the cathode terminal (for example, in the first embodiment). Cathode terminal).

  The first transistor M1 is configured to selectively supply the data voltage Vdata supplied from the data line D to the first terminal of the first capacitor 21. The second transistor M2 selects the first power supply voltage VDD supplied from the first power supply line P1 as the first terminal of the third transistor M3, the second terminal of the first capacitor 21, and the second terminal of the second capacitor 22. It is comprised so that it may supply. The third transistor M3 is configured to selectively connect the second terminal of the first capacitor 21 and the second terminal of the second capacitor 22 to the first terminal of the fourth transistor M4. The fourth transistor M4 is configured to selectively connect the second terminal of the third transistor M3 to the first terminal of the light emitting element 11. The fifth transistor M5 is configured to selectively supply the third power supply voltage Vref corresponding to the above-described reference voltage (Vref) to the first terminal of the first capacitor 21 while being supplied from the third power supply line P3. Has been. The sixth transistor M6 is configured to selectively supply the third power supply voltage Vref supplied from the third power supply line P3 to the second terminal of the third transistor M3. The second power supply line P2 supplies, for example, a second power supply voltage VSS, which is a ground potential, to the second terminal of the light emitting element 11.

  The first to sixth transistors M1 to M6 are p-channel transistors, and more specifically, p-channel TFTs. The light emitting element 11 is an OLED. In general, an OLED has a substrate side (VSS side) as a cathode. Therefore, in order to connect the anode to the drain of the drive transistor, the drive transistor needs to be a p-channel type. If it does so, even if the resistance value of OLED changes with progress of time, a constant current can always be supplied to OLED.

  The first, second, fourth, fifth, and sixth transistors M1, M2, M4, M5, and M6 constituting the switch unit 13 are switching transistors that operate in a linear region. The third transistor M3 is an amplifying transistor that operates in a saturation region.

  FIG. 2 is a plan view illustrating a display device including the pixel circuit according to the first embodiment. Hereinafter, description will be given based on this drawing.

  The display device 30 in the first embodiment is an AMOLED. The display device 30 is roughly divided into a TFT substrate 100 in which a plurality of pixel circuits including light emitting elements (see FIG. 1A) are arranged in a matrix, a sealing glass substrate 200 for sealing the light emitting elements, and the TFT substrate 100. The glass frit seal part 300 etc. which join the sealing glass substrate 200 are comprised. Further, around the cathode electrode formation region 114a outside the active matrix portion 116 of the TFT substrate 100, there is a scan driver 131 that drives the scanning lines (each control line) of the TFT substrate 100, and an emission that controls the light emission period of each pixel. A control driver 132, a data line ESD (Electro-Static-Discharge) protection circuit 133 for preventing damage due to electrostatic discharge, a demultiplexer 134 for returning a high transfer rate stream to a plurality of original low transfer rate streams, and driving the data line A data driver IC 135 and the like are arranged. The data driver IC 135 is mounted on the TFT substrate 100 using an anisotropic conductive film. The TFT substrate 100 is connected to an external device via an FPC (Flexible Printed Circuit) 136. FIG. 2 is an example of the display device according to the first embodiment, and the shape and configuration thereof can be changed as appropriate.

  The correspondence between FIG. 1A and FIG. 2 is as follows. The first control line S1 and the fourth control line S4 in FIG. 1A are connected to the scan driver 131 in FIG. The second control line S2 and the third control line S3 in FIG. 1A are connected to the emission control driver 132 in FIG. The data line D in FIG. 1A is connected to the demultiplexer 134 and the data driver IC 135 in FIG. The first to third power supply lines P1 to P3 in FIG. 1A are connected to an external power supply via the FPC 136 in FIG.

  FIG. 3 is an enlarged cross-sectional view of a part of FIG. Hereinafter, description will be given based on this drawing.

  The TFT substrate 100 is formed on a glass substrate 101 through a base insulating film 102 and a polysilicon layer 103 made of low temperature polysilicon (LTPS) or the like, and a gate insulating film 104. A first metal layer 105 (gate electrode and capacitor electrode) and a second metal layer 107 (data line, power supply line, source and drain electrode) connected to the polysilicon layer 103 through an opening formed in the interlayer insulating film 106 , A contact portion) and a light emitting element 11 (an anode electrode 111, an organic EL layer 113, a cathode electrode 114, and a cap layer 115) formed in a recess of the element isolation film 112 via the planarizing film 110.

  The polysilicon layer 103 in the TFT region 108 has an LDD (Lightly Doped Drain) structure, and is a p + layer, a p− layer, an i layer, a p− layer, and a p + layer from the left. The polysilicon layer 103 in the capacitor region 109 is a p + layer.

  Dry air 301 is sealed between the light emitting element 11 and the sealing glass substrate 200, and these are sealed by the glass frit seal portion 300 (FIG. 2), whereby the display device 30 is formed. The light emitting element 11 has a top emission structure. The light emitting element 11 and the sealing glass substrate 200 are set at a predetermined interval, and a λ / 4 retardation plate 201 is provided on the light emission surface side of the sealing glass substrate 200. A polarizing plate 202 is formed, and reflection of light incident from the outside is suppressed.

  3 shows a top emission structure in which each radiated light of the light emitting element 11 is radiated to the outside through the sealing glass substrate 200, a bottom emission structure to be radiated to the outside through the glass substrate 101. It can also be.

  4A to 7B show the operation (driving method) of the pixel circuit of Embodiment 1, and FIGS. 4A, 5A, 6A, and 7A are circuit diagrams in the first to fourth periods, and FIG. 4B and FIG. 5B, FIG. 6B, and FIG. 7B are timing diagrams in the first to fourth periods. Hereinafter, the operation (driving method) of the pixel circuit of Embodiment 1 will be described by adding FIGS. 4A to 7B to FIG. 1A and FIG. 1B.

  4A, FIG. 5A, FIG. 6A, and FIG. 7A, a part of the reference numerals attached in FIG. 1A is omitted for easy understanding. In FIG. 4A, FIG. 5A, FIG. 6A, and FIG. 7A, “x” marks indicate transistors that are off. Since the pixel circuit operates according to the driving method of the pixel circuit, the operation (driving method) of the pixel circuit is described.

  First, an outline of a driving method of the pixel circuit 10 will be described with reference to FIGS. 1A and 1B. The driving method of the pixel circuit 10 includes the following first to fourth periods T1 to T4. At this time, the switch unit 13 operates as follows.

In the first period T1, the voltage held in the capacitor unit 12 is initialized.
In the second period T2 after the first period T1, the current bypassing transistor (M6) and the reference voltage transistor (M5) are turned on to hold the voltage including the threshold voltage Vth of the driving transistor (M1) in the capacitor unit 12. Let
In the third period T3 after the second period T2, the data voltage transistor (M1) is turned on, the data voltage Vdata is supplied to the capacitor unit 12, and the voltage including the threshold voltage Vth and the data voltage Vdata is supplied to the capacitor unit. 12 to hold.
In a fourth period T4 after the third period T3, a voltage corresponding to the data voltage Vdata is supplied to the light emitting element 11 by applying a voltage held in the capacitor unit 12 to the driving transistor (M3).

More specifically, the voltage held in the capacitor unit 12 is initialized in the first period T1.
In the second period T2, the voltage including the threshold voltage Vth of the drive transistor (M3) is turned on by turning on the current bypass transistor (M6) and the reference voltage transistor (M5) and turning off the data voltage transistor (M1). Is held by the capacitor unit 12.
In the third period T3, by turning off the current bypass transistor (M6) and the reference voltage transistor (M5) and turning on the data voltage transistor (M1), the data voltage Vdata is supplied to the capacitor unit 12, Voltage including the threshold voltage Vth and the data voltage Vdata is held in the capacitor unit 12.
In the fourth period T4, a voltage corresponding to the data voltage Vdata is supplied to the light emitting element 11 by applying a voltage held by the capacitor unit 12 between the gate terminal and the source terminal of the driving transistor (M3).

  Further, in the first period T1, the voltage held in the capacitor unit 12 is initialized, the driving transistor (M3) and the current bypass transistor (M6) are turned on, and a current is passed through the driving transistor (M3). The current may be supplied to the reference voltage power supply line (P3) without flowing to the light emitting element 11 via the current bypass transistor (M6).

  Next, each period will be described in detail.

  In the first period T1 shown in FIGS. 4A and 4B, the first transistor M1 and the fourth transistor M4 are turned off, and the second transistor M2, the third transistor M3, the fifth transistor M5, and the sixth transistor M6 are turned on. The voltages of the first to fourth control lines S1 to S4 are set.

At this time, the voltage VA at the node A becomes the third power supply voltage Vref via the fifth transistor M5, and the voltage VB at the node B becomes the first power supply voltage VDD via the second transistor M2. That is, the voltage VA at the node A and the voltage VB at the node B are expressed by the following equations, and the voltages held in the first and second capacitors 21 and 22 are initialized.
VA = Vref
VB = VDD

  On the other hand, when the third transistor M3 and the sixth transistor M6 are turned on, the current i1 flows to the third transistor M3, and the current i1 does not flow to the light emitting element 11 via the sixth transistor M6. It flows to P3.

At this time, since the voltage applied between the gate terminal and the source terminal of the third transistor M3 is VB-VA, the current i1 flowing through the drain terminal is given by the following equation.
i1 = 1 / 2β ((VB−VA) −Vth) ²
= 1 / 2β (VDD−Vref−Vth) ²

  As can be seen from the above equation, since the current i1 is a sufficiently large value on the order of the white display level, initialization of the hysteresis characteristics of the third transistor M3 is prevented. This is the image retention prevention function of the pixel circuit 10. In the above equation, β is a constant determined by the structure and material of the third transistor M3.

  In the second period T2 shown in FIGS. 5A and 5B, the first transistor M1 and the second transistor M2 are turned off, and the third transistor M3, the fourth transistor M4, the fifth transistor M5, and the sixth transistor M6 are turned on. The voltages of the first to fourth control lines S1 to S4 are set.

At this time, the voltage VA of the node A becomes the third power supply voltage Vref via the fifth transistor M5. Therefore, since the electric charge held in the first and second capacitors 21 and 22 is discharged through the third transistor M3 and the sixth transistor M6, the current i2 flows from the third transistor M3. VB decreases from the first power supply voltage VDD. When the voltage VB at the node B decreases to Vref + Vth, the third transistor M3 is turned off. That is, the voltage VA at the node A and the voltage VB at the node B are expressed by the following equations, and the voltage including the threshold voltage Vth of the third transistor M3 is held in the first and second capacitors 21 and 22. Thus, in the first embodiment, source follower type threshold voltage detection is used.
VA = Vref
VB = Vref + Vth

  The third power supply voltage Vref, which is a reference voltage necessary for threshold voltage detection, is supplied from a third power supply line P3 different from the data line D through the fifth transistor M5. Therefore, since the threshold voltage is not affected by the data line D, in principle, no crosstalk occurs. Therefore, the threshold voltage Vth can be detected in a time corresponding to N (natural number) × H (horizontal scanning period). Therefore, since the threshold voltage Vth can be detected in a sufficient time, an accurate threshold voltage Vth can be obtained, so that the compensation performance of the threshold voltage Vth is high. In the first embodiment, N = 2.

  Further, the current i2 that flows when the third transistor M3, which is a driving transistor, is temporarily turned on when the threshold voltage is detected does not flow to the light emitting element 11 via the sixth transistor M6, but flows to the third power supply line P3. For this reason, since no current is supplied to the light emitting element 11 when the threshold voltage is detected, it is possible to prevent a decrease in contrast due to leakage light emission. This is the function for preventing the contrast reduction of the pixel circuit 10.

  In the third period T3 shown in FIGS. 6A and 6B, the second transistor M2, the fourth transistor M4, the fifth transistor M5, and the sixth transistor M6 are turned off, and the first transistor M1 and the third transistor M3 are turned on. Are set to voltages of the first to fourth control lines S1 to S4, and a data voltage Vdata is supplied from the data line D.

At this time, the voltage VA of the node A becomes the data voltage Vdata through the first transistor M1. On the other hand, assuming that the capacitance values of the first and second capacitors 21 and 22 are C1 and C2, respectively, the voltage VB of the node B is K (Vdata) which is a divided voltage of the first and second capacitors 21 and 22 connected in series. −Vref) is increased to the following equation. That is, by supplying the data voltage Vdata to the first and second capacitors 21 and 22, a voltage including the threshold voltage Vth and the data voltage Vdata is held in the first and second capacitors 21 and 22.
VA = Vdata
VB = Vref + Vth + K (Vdata−Vref)
K = C1 / (C1 + C2)
Here, C1 <C2, that is, K <1/2. The reason for this is to increase the term of Vdata applied to the third transistor M3, as can be seen from the equation described later.

  In the fourth period T4 shown in FIGS. 7A and 7B, the first transistor M1, the fifth transistor M5, and the sixth transistor M6 are turned off, and the second transistor M2, the third transistor M3, and the fourth transistor M4 are turned on. The voltages of the first to fourth control lines S1 to S4 are set.

At this time, the voltage VB at the node B becomes the first power supply voltage VDD via the second transistor M2. On the other hand, the voltage VA at the node A is obtained by subtracting the voltage VB in the third period T3 from the first power supply voltage VDD and adding it to the voltage VA in the third period T3 as follows.
VA = Vdata + (VDD−Vref−Vth−K (Vdata−Vref))
= (1-K) Vdata + (K-1) Vref-Vth + VDD
VB = VDD

Thus, since the voltage applied between the gate terminal and the source terminal of the third transistor M3 is VB-VA, the current I flowing through the drain terminal is given by the following equation.
I = 1 / 2β ((VB−VA) −Vth) ²
= 1 / 2β (VDD − ((1−K) Vdata + (K−1) Vref−Vth + VDD) −Vth) ²
= 1 / 2β ((1-K) Vref− (1-K) Vdata) ²

  As can be seen from the above equation, the current I does not include the term of the threshold voltage Vth, and therefore is not affected by variations and fluctuations in the threshold voltage Vth. This is the threshold voltage Vth variation compensation function of the pixel circuit 10.

  As described above, in the fourth period T4, the voltage held by the first and second capacitors 21 and 22 is applied between the gate terminal and the source terminal of the third transistor M3, so that the data voltage Vdata is satisfied. The supplied current I is supplied to the light emitting element 11.

  Note that VDD> Vref> VSS is established, and for example, VDD = 10V, VSS = 0V, Vref = 7 to 8V, and Vdata = 1 to 6V.

  In other words, the effects of the first embodiment are as follows. 1) Since the current flowing at the time of reset is bypassed and does not flow to the OLED, the contrast is not lowered in principle. 2) By causing a current to flow through the OLED driving transistor each time the OLED is driven, the problem of image retention does not occur. 3) Since the circuit can control the threshold voltage detection period independently, the threshold voltage can be detected accurately with a sufficiently long time. Therefore, the display unevenness compensation capability is high, and more uniform display characteristics can be obtained. 4) Since it is not affected by the change of the data signal during the threshold voltage detection period, in principle, no crosstalk occurs. 5) As described above, contrast reduction and image retention do not occur, compensation capability for variations and fluctuations in threshold voltage is high, and crosstalk does not occur, so that high image quality can be realized. Further, as will be described later, since the demultiplexer can be easily applied, the number of output pins of the data driver IC can be reduced, which is practical.

<Embodiment 2>
FIG. 8A is a circuit diagram illustrating a part of the display device according to the second embodiment, and FIG. 8B is a timing diagram illustrating an operation of the display device according to the third embodiment. Hereinafter, description will be given based on these drawings.

  The display device according to the second embodiment is characterized by a demultiplexer 134. The demultiplexer 134 shown in FIG. 8A is for one pixel. In the case where the pixel circuit of Embodiment 1 is a sub-pixel, one pixel is composed of three RGB sub-pixels. Each pixel circuit has, for example, an RGB vertical stripe type arrangement structure.

  The demultiplexer 134 sequentially selects one data line from among the three data lines Dnr, Dng, and Dnb respectively connected to the three pixel circuits, and supplies the selected one data line to the data voltage Vdata. Connected to another data line Dn connected to the source (data driver IC 135 shown in FIG. 2). The data lines Dnr, Dng, and Dnb correspond to the data line D in FIG. 1A, respectively.

  The demultiplexer 134 has three switching transistors Mnr, Mng, and Mnb per pixel. The transistors Mnr, Mng, and Mnb selectively connect the three data lines Dnr, Dng, and Dnb to the single data line Dn by the fifth control signals R_set, G_set, and G_set, respectively. The data voltage Rn is output from the data line Dn to the data line Dnr via the transistor Mnr, the data voltage Rg is output to the data line Dng via the transistor Mng, and the data voltage Rb is output to the data line Dnb via the transistor Mnb. Is output.

  The fifth control signals R_set, G_set, and G_set are output within one horizontal scanning period 1H at different times so as not to overlap each other. After the data voltages Rr, Rg, Rb of all the data lines Dnr, Dng, Dnb are determined, the transistor M1 (FIG. 1A) is turned on. By using the demultiplexer 134, the total number of data lines D of the data driver IC 135 (FIG. 2) can be reduced.

  In an existing pixel circuit using a demultiplexer that divides a data voltage output from one data line into three data lines, both threshold voltage detection and data writing must be within one horizontal scanning period. . However, when the horizontal scanning period is shortened due to an increase in the number of scanning lines accompanying the increase in definition, the writing time per data line is shortened and data writing becomes insufficient.

  On the other hand, in the display device according to the second embodiment, by using the pixel circuit according to the first embodiment, almost the entire one horizontal scanning period 1H (third period T3) can be used for data writing by the demultiplexer 134. In addition, the pulse widths of the fifth control signals R_set, G_set, and G_set can be taken sufficiently, thereby improving the display performance.

  Other configurations, operations, and effects of the second embodiment are the same as those of the first embodiment.

<Summary>
As described above, the present invention has been described with reference to each of the above embodiments, but the present invention is not limited only to the configuration and operation of each of the above embodiments, and can be made by those skilled in the art within the scope of the present invention. Of course, it includes various variations and modifications that can be made. Further, the present invention includes a combination of some or all of the configurations of the above-described embodiments as appropriate.

  For example, in the embodiments, all transistors are p-channel type, but this is not limiting, and some or all of the transistors may be n-channel type. At this time, when the driving transistor of the OLED is an n-channel type, the conduction direction of the OLED is reversed so that the cathode terminal of the OLED is connected to the drain terminal. The semiconductor material forming the transistor is not limited to silicon such as LTPS, and an oxide semiconductor such as IGZO (Indium Gallium Zinc Oxide) may be used. In addition, the switch unit has a source follower type threshold voltage detection structure, but may have a diode connection type threshold voltage detection structure.

  Although a part or all of the above embodiments can be described as the following supplementary notes, the present invention is not limited to the following configurations.

[Appendix 1] a light emitting device;
A drive transistor for supplying a current corresponding to the applied voltage to the light emitting element;
A capacitor unit that holds a voltage including a threshold voltage and a data voltage of the driving transistor and applies the voltage to the driving transistor;
A switch unit that holds the voltage including the threshold voltage and the data voltage in the capacitor unit;
In a pixel circuit comprising:
The switch unit includes a current bypass transistor that bypasses the current supplied from the drive transistor to a reference voltage power line without passing through the light emitting element.
A pixel circuit characterized by that.

[Appendix 2] In the pixel circuit described in Appendix 1,
The switch unit turns on the driving transistor and the current bypass transistor before holding the voltage including the threshold voltage and the data voltage in the capacitor unit.
A pixel circuit characterized by that.

[Appendix 3] In the pixel circuit according to Appendix 1 or 2,
The switch section further includes a reference voltage transistor for inputting a reference voltage from the reference voltage power supply line, and a data voltage transistor for inputting the data voltage from a data line.
A pixel circuit characterized by that.

[Appendix 4] In the pixel circuit described in Appendix 3,
The driving transistor has a gate terminal, a source terminal, and a drain terminal, and supplies a current corresponding to a voltage applied between the gate terminal and the source terminal to the light emitting element connected to the drain terminal. And
The capacitor unit holds a voltage including the threshold voltage and the data voltage, and applies this voltage between the gate terminal and the source terminal of the driving transistor,
The switch part is
A plurality of transistors including the current bypass transistor, the reference voltage transistor, and the data voltage transistor, and the switching operation of these transistors causes the capacitor unit to hold a voltage including the threshold voltage; Holding a voltage including the threshold voltage and the data voltage, and
When the voltage including the threshold voltage is held in the capacitor unit, the reference voltage is supplied to the capacitor unit by turning on the current bypass transistor and the reference voltage transistor and turning off the data voltage transistor. Supply
When holding the voltage including the threshold voltage and the data voltage in the capacitor unit, the data voltage is reduced by turning off the current bypass transistor and the reference voltage transistor and turning on the data voltage transistor. Supplying to the capacitor unit,
A pixel circuit characterized by that.

[Appendix 5] In the pixel circuit described in Appendix 4,
The switch part is
When holding the voltage including the threshold voltage in the capacitor unit, by turning on the current bypass transistor and the reference voltage transistor and turning off the data voltage transistor over a time of one horizontal scanning period or more, Supplying the reference voltage to the capacitor unit;
A pixel circuit characterized by that.

[Appendix 6] In the pixel circuit described in Appendix 4 or 5,
The switch part is
When the voltage including the threshold voltage is held in the capacitor unit, the drive transistor is temporarily turned on by turning on the current bypass transistor and supplying the reference voltage to the capacitor unit.
A pixel circuit characterized by that.

[Appendix 7] In the pixel circuit according to any one of appendices 4 to 6,
Electrically connected to the data line, the first to fourth control lines, and the first to third power lines, and includes first to sixth transistors, first to second capacitors, and the light emitting element;
The third power supply line corresponds to the reference voltage power supply line, the first, second, fourth, fifth and sixth transistors constitute the switch unit, and the first transistor serves as the data voltage transistor. The fifth transistor corresponds to the reference voltage transistor, the sixth transistor corresponds to the current bypass transistor, the third transistor corresponds to the drive transistor, and the first and second capacitors. Constitutes the capacitor part,
The first transistor has a first terminal electrically connected to the data line, a second terminal, and a control terminal electrically connected to the first control line,
The second transistor has a first terminal electrically connected to the first power supply line, a second terminal, and a control terminal electrically connected to the second control line,
The third transistor is electrically connected to the second terminal of the second transistor and has a first terminal corresponding to the source terminal, a second terminal corresponding to the drain terminal, and a first terminal of the first transistor. A control terminal electrically connected to the second terminal and corresponding to the gate terminal;
The fourth transistor has a first terminal electrically connected to the second terminal of the third transistor, a second terminal, and a control terminal electrically connected to the third control line. ,
The fifth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the first transistor, and a fourth control line. A control terminal electrically connected,
The sixth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the third transistor, and a fourth control line. A control terminal electrically connected,
The first capacitor has a first terminal electrically connected to the second terminal of the first transistor and a second terminal electrically connected to the first terminal of the third transistor. ,
The second capacitor has a first terminal connected to the third power supply line, and a second terminal electrically connected to the first terminal of the third transistor,
The light emitting element has a first terminal electrically connected to the second terminal of the fourth transistor, and a second terminal electrically connected to the second power line.
A pixel circuit characterized by that.

[Appendix 8] In the pixel circuit described in Appendix 7,
The first transistor is configured to selectively supply the data voltage supplied from the data line to the first terminal of the first capacitor;
The second transistor supplies a first power supply voltage supplied from the first power supply line to the first terminal of the third transistor, the second terminal of the first capacitor, and the second terminal of the second capacitor. Configured to selectively supply to
The third transistor is configured to selectively connect the second terminal of the first capacitor and the second terminal of the second capacitor to the first terminal of the fourth transistor;
The fourth transistor is configured to selectively connect the second terminal of the third transistor to the first terminal of the light-emitting element;
The fifth transistor is configured to selectively supply a third power supply voltage corresponding to the reference voltage supplied from the third power supply line to the first terminal of the first capacitor,
The sixth transistor is configured to selectively supply a third power supply voltage corresponding to the reference voltage to the second terminal of the third transistor while being supplied from the third power supply line.
A pixel circuit characterized by that.

[Supplementary Note 9] A pixel circuit that is electrically connected to the data line, the first to fourth control lines, and the first to third power supply lines and includes first to sixth transistors, first to second capacitors, and a light emitting element Because
The first transistor has a first terminal electrically connected to the data line, a second terminal, and a control terminal electrically connected to the first control line,
The second transistor has a first terminal electrically connected to the first power supply line, a second terminal, and a control terminal electrically connected to the second control line,
The third transistor includes a first terminal electrically connected to the second terminal of the second transistor, a second terminal, and a control terminal electrically connected to the second terminal of the first transistor. And
The fourth transistor has a first terminal electrically connected to the second terminal of the third transistor, a second terminal, and a control terminal electrically connected to the third control line. ,
The fifth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the first transistor, and a fourth control line. A control terminal electrically connected,
The sixth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the third transistor, and a fourth control line. A control terminal electrically connected,
The first capacitor has a first terminal electrically connected to the second terminal of the first transistor and a second terminal electrically connected to the first terminal of the third transistor. ,
The second capacitor has a first terminal connected to the third power supply line, and a second terminal electrically connected to the first terminal of the third transistor,
The light emitting element has a first terminal electrically connected to the second terminal of the fourth transistor, and a second terminal electrically connected to the second power line.
A pixel circuit characterized by that.

[Appendix 10] In the pixel circuit described in Appendix 9,
The first transistor is configured to selectively supply a data voltage supplied from the data line to the first terminal of the first capacitor;
The second transistor supplies a first power supply voltage supplied from the first power supply line to the first terminal of the third transistor, the second terminal of the first capacitor, and the second terminal of the second capacitor. Configured to selectively supply to
The third transistor is configured to selectively connect the second terminal of the first capacitor and the second terminal of the second capacitor to the first terminal of the fourth transistor;
The fourth transistor is configured to selectively connect a second terminal of the third transistor to the first terminal of the light emitting element,
The fifth transistor is configured to selectively supply a third power supply voltage supplied from the third power supply line to the first terminal of the first capacitor,
The sixth transistor is configured to selectively supply a third power supply voltage supplied from the third power supply line to the second terminal of the third transistor.
A pixel circuit characterized by that.

[Appendix 11] In the pixel circuit according to any one of Appendixes 7 to 10,
The first to sixth transistors are p-channel transistors.
A pixel circuit characterized by that.

[Supplementary Note 12] In the pixel circuit according to any one of Supplementary notes 1 to 11,
The light emitting element is an organic light emitting diode,
A pixel circuit characterized by that.

[Supplementary note 13] The pixel circuit according to any one of the supplementary notes 1 to 12 arranged in a matrix.
A display device comprising:

[Supplementary Note 14] In the display device according to Supplementary Note 13,
In the case where the pixel circuit is a sub-pixel, when one pixel is composed of two or more constant sub-pixels, one of the data lines connected to a certain number of the pixel circuits is connected to one pixel line. A demultiplexer that sequentially selects data lines and connects the selected one data line to another data line connected to the data voltage supply source,
A display device further comprising the display device.

[Supplementary Note 15] A method of driving the pixel circuit according to Supplementary Note 3, including the first to fourth periods,
The switch part is
In the first period, initialize the voltage held in the capacitor unit,
In the second period after the first period, the current bypass transistor and the reference voltage transistor are turned on to hold the voltage including the threshold voltage of the driving transistor in the capacitor unit,
In the third period after the second period, the data voltage transistor is turned on, the data voltage is supplied to the capacitor unit, and a voltage including the threshold voltage and the data voltage is supplied to the capacitor unit. Hold
Supplying a current corresponding to the data voltage to the light emitting element by applying a voltage held in the capacitor unit to the driving transistor in the fourth period after the third period;
A driving method of a pixel circuit.

[Supplementary Note 16] A method for driving the pixel circuit according to any one of Supplementary notes 3 to 6, including the first to fourth periods,
The switch part is
In the first period, initialize the voltage held in the capacitor unit,
By turning on the current bypass transistor and the reference voltage transistor and turning off the data voltage transistor in the second period after the first period, a voltage including the threshold voltage of the driving transistor is obtained. Holding the capacitor part,
In the third period after the second period, the data voltage is supplied to the capacitor unit by turning off the current bypass transistor and the reference voltage transistor and turning on the data voltage transistor. , Holding the voltage including the threshold voltage and the data voltage in the capacitor unit,
In the fourth period after the third period, by applying a voltage held in the capacitor unit between the gate terminal and the source terminal of the driving transistor, the current corresponding to the data voltage is emitted. Supply to the element,
A driving method of a pixel circuit.

[Supplementary Note 17] In the pixel circuit driving method according to Supplementary Note 15 or 16,
The switch unit initializes the voltage held in the capacitor unit in the first period, turns on the driving transistor and the current bypass transistor, and causes a current to flow to the driving transistor. Without flowing to the light emitting element via the current bypass transistor, to flow to the reference voltage power supply line,
A driving method of a pixel circuit.

[Appendix 18] A method for driving the pixel circuit according to any one of Appendixes 7 to 12, including the first to fourth periods,
In the first period, the first to fourth transistors are turned off so that the second transistor, the third transistor, the fifth transistor, and the sixth transistor are turned on. Set the control line voltage,
In the second period after the first period, the first transistor and the second transistor are turned off, and the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are turned on. To set the voltage of the first to fourth control lines,
In the third period after the second period, the second transistor, the fourth transistor, the fifth transistor, and the sixth transistor are turned off, and the first transistor and the third transistor are turned on. And setting the voltage of the first to fourth control lines, and supplying the data voltage from the data line,
In the fourth period after the third period, the first transistor, the fifth transistor, and the sixth transistor are turned off, and the second transistor, the third transistor, and the fourth transistor are turned on. A voltage of the first to fourth control lines is set to
A driving method of a pixel circuit.

[Supplementary note 19] In the pixel circuit driving method according to any one of supplementary notes 15 to 18,
The second period is a time longer than one horizontal scanning period.
A driving method of a pixel circuit.

<Embodiment 1>
DESCRIPTION OF SYMBOLS 10 Pixel circuit 11 Light emitting element 12 Capacitor part 13 Switch part 21 1st capacitor 22 2nd capacitor M1 1st transistor (transistor for data voltage)
M2 Second transistor M3 Third transistor M4 Fourth transistor M5 Fifth transistor (reference voltage transistor)
M6 6th transistor (current bypass transistor)
D data line P1 first power supply line P2 second power supply line P3 third power supply line S1 first control line S2 second control line S3 third control line S4 fourth control line A, B node Vdata data voltage VDD first power supply voltage VSS Second power supply voltage Vref Third power supply voltage (reference voltage)
Scan First control signal EM Second control signal BP Third control signal Reset Fourth control signal 30 Display device 100 TFT substrate 101 Glass substrate 102 Base insulating film 103 Polysilicon layer 104 Gate insulating film 105 First metal layer 106 Interlayer insulating film 107 Second metal layer 108 TFT region 109 Capacitor region 110 Planarization film 111 Anode electrode 112 Element isolation film 113 Organic EL layer 114 Cathode electrode 114a Cathode electrode formation region 115 Cap layer 116 Active matrix part 131 Scan driver 132 Emission control driver 133 Data Line ESD protection circuit 134 Demultiplexer 135 Data driver IC
136 FPC
200 Sealing glass substrate 201 λ / 4 retardation plate 202 Polarizing plate 300 Glass frit seal portion 301 Dry air <Embodiment 2>
Dn, Dnr, Dng, Dnb Data lines Mnr, Mng, Mnb Transistors Rr, Rg, Rb Data voltage R_set, G_set, G_set Fifth control signal <Related technology>
900 Pixel circuit 901 Switch TFT
902 Drive TFT
903 capacitor 904 OLED
905 Scan line 906 Data line 907, 908 Power supply line

In the second period T2 shown in FIGS. 5A and 5B, the first transistor M1 , the second transistor M2, and the fourth transistor M4 are turned off, and the third transistor M3 , the fifth transistor M5, and the sixth transistor M6 are turned on. The voltages of the first to fourth control lines S1 to S4 are set.

Claims (19)

A light emitting element;
A drive transistor for supplying a current corresponding to the applied voltage to the light emitting element;
A capacitor unit that holds a voltage including a threshold voltage and a data voltage of the driving transistor and applies the voltage to the driving transistor;
A switch unit that holds the voltage including the threshold voltage and the data voltage in the capacitor unit;
In a pixel circuit comprising:
The switch unit includes a current bypass transistor that bypasses the current supplied from the drive transistor to a reference voltage power line without passing through the light emitting element.
A pixel circuit characterized by that. The pixel circuit according to claim 1.
The switch unit turns on the driving transistor and the current bypass transistor before holding the voltage including the threshold voltage and the data voltage in the capacitor unit.
A pixel circuit characterized by that. The pixel circuit according to claim 1 or 2,
The switch section further includes a reference voltage transistor for inputting a reference voltage from the reference voltage power supply line, and a data voltage transistor for inputting the data voltage from a data line.
A pixel circuit characterized by that. The pixel circuit according to claim 3.
The driving transistor has a gate terminal, a source terminal, and a drain terminal, and supplies a current corresponding to a voltage applied between the gate terminal and the source terminal to the light emitting element connected to the drain terminal. And
The capacitor unit holds a voltage including the threshold voltage and the data voltage, and applies this voltage between the gate terminal and the source terminal of the driving transistor,
The switch part is
A plurality of transistors including the current bypass transistor, the reference voltage transistor, and the data voltage transistor, and the switching operation of these transistors causes the capacitor unit to hold a voltage including the threshold voltage; Holding a voltage including the threshold voltage and the data voltage, and
When the voltage including the threshold voltage is held in the capacitor unit, the reference voltage is supplied to the capacitor unit by turning on the current bypass transistor and the reference voltage transistor and turning off the data voltage transistor. Supply
When holding the voltage including the threshold voltage and the data voltage in the capacitor unit, the data voltage is reduced by turning off the current bypass transistor and the reference voltage transistor and turning on the data voltage transistor. Supplying to the capacitor unit,
A pixel circuit characterized by that. The pixel circuit according to claim 4.
The switch part is
When holding the voltage including the threshold voltage in the capacitor unit, by turning on the current bypass transistor and the reference voltage transistor and turning off the data voltage transistor over a time of one horizontal scanning period or more, Supplying the reference voltage to the capacitor unit;
A pixel circuit characterized by that. The pixel circuit according to claim 4 or 5,
The switch part is
When the voltage including the threshold voltage is held in the capacitor unit, the drive transistor is temporarily turned on by turning on the current bypass transistor and supplying the reference voltage to the capacitor unit.
A pixel circuit characterized by that. The pixel circuit according to any one of claims 4 to 6,
Electrically connected to the data line, the first to fourth control lines, and the first to third power lines, and includes first to sixth transistors, first to second capacitors, and the light emitting element;
The third power supply line corresponds to the reference voltage power supply line, the first, second, fourth, fifth and sixth transistors constitute the switch unit, and the first transistor serves as the data voltage transistor. The fifth transistor corresponds to the reference voltage transistor, the sixth transistor corresponds to the current bypass transistor, the third transistor corresponds to the drive transistor, and the first and second capacitors. Constitutes the capacitor part,
The first transistor has a first terminal electrically connected to the data line, a second terminal, and a control terminal electrically connected to the first control line,
The second transistor has a first terminal electrically connected to the first power supply line, a second terminal, and a control terminal electrically connected to the second control line,
The third transistor is electrically connected to the second terminal of the second transistor and has a first terminal corresponding to the source terminal, a second terminal corresponding to the drain terminal, and a first terminal of the first transistor. A control terminal electrically connected to the second terminal and corresponding to the gate terminal;
The fourth transistor has a first terminal electrically connected to the second terminal of the third transistor, a second terminal, and a control terminal electrically connected to the third control line. ,
The fifth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the first transistor, and a fourth control line. A control terminal electrically connected,
The sixth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the third transistor, and a fourth control line. A control terminal electrically connected,
The first capacitor has a first terminal electrically connected to the second terminal of the first transistor and a second terminal electrically connected to the first terminal of the third transistor. ,
The second capacitor has a first terminal connected to the third power supply line, and a second terminal electrically connected to the first terminal of the third transistor,
The light emitting element has a first terminal electrically connected to the second terminal of the fourth transistor, and a second terminal electrically connected to the second power line.
A pixel circuit characterized by that. The pixel circuit according to claim 7.
The first transistor is configured to selectively supply the data voltage supplied from the data line to the first terminal of the first capacitor;
The second transistor supplies a first power supply voltage supplied from the first power supply line to the first terminal of the third transistor, the second terminal of the first capacitor, and the second terminal of the second capacitor. Configured to selectively supply to
The third transistor is configured to selectively connect the second terminal of the first capacitor and the second terminal of the second capacitor to the first terminal of the fourth transistor;
The fourth transistor is configured to selectively connect the second terminal of the third transistor to the first terminal of the light-emitting element;
The fifth transistor is configured to selectively supply a third power supply voltage corresponding to the reference voltage supplied from the third power supply line to the first terminal of the first capacitor,
The sixth transistor is configured to selectively supply a third power supply voltage corresponding to the reference voltage to the second terminal of the third transistor while being supplied from the third power supply line.
A pixel circuit characterized by that. A pixel circuit electrically connected to the data line, the first to fourth control lines, and the first to third power supply lines and including first to sixth transistors, first to second capacitors, and a light emitting element;
The first transistor has a first terminal electrically connected to the data line, a second terminal, and a control terminal electrically connected to the first control line,
The second transistor has a first terminal electrically connected to the first power supply line, a second terminal, and a control terminal electrically connected to the second control line,
The third transistor includes a first terminal electrically connected to the second terminal of the second transistor, a second terminal, and a control terminal electrically connected to the second terminal of the first transistor. And
The fourth transistor has a first terminal electrically connected to the second terminal of the third transistor, a second terminal, and a control terminal electrically connected to the third control line. ,
The fifth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the first transistor, and a fourth control line. A control terminal electrically connected,
The sixth transistor includes a first terminal electrically connected to the third power supply line, a second terminal electrically connected to the second terminal of the third transistor, and a fourth control line. A control terminal electrically connected,
The first capacitor has a first terminal electrically connected to the second terminal of the first transistor and a second terminal electrically connected to the first terminal of the third transistor. ,
The second capacitor has a first terminal connected to the third power supply line, and a second terminal electrically connected to the first terminal of the third transistor,
The light emitting element has a first terminal electrically connected to the second terminal of the fourth transistor, and a second terminal electrically connected to the second power line.
A pixel circuit characterized by that. The pixel circuit according to claim 9.
The first transistor is configured to selectively supply a data voltage supplied from the data line to the first terminal of the first capacitor;
The second transistor supplies a first power supply voltage supplied from the first power supply line to the first terminal of the third transistor, the second terminal of the first capacitor, and the second terminal of the second capacitor. Configured to selectively supply to
The third transistor is configured to selectively connect the second terminal of the first capacitor and the second terminal of the second capacitor to the first terminal of the fourth transistor;
The fourth transistor is configured to selectively connect a second terminal of the third transistor to the first terminal of the light emitting element,
The fifth transistor is configured to selectively supply a third power supply voltage supplied from the third power supply line to the first terminal of the first capacitor,
The sixth transistor is configured to selectively supply a third power supply voltage supplied from the third power supply line to the second terminal of the third transistor.
A pixel circuit characterized by that. The pixel circuit according to any one of claims 7 to 10,
The first to sixth transistors are p-channel transistors.
A pixel circuit characterized by that. The pixel circuit according to claim 1,
The light emitting element is an organic light emitting diode,
A pixel circuit characterized by that. A plurality of pixel circuits according to any one of claims 1 to 12 arranged in a matrix.
A display device comprising: The display device according to claim 13,
In the case where the pixel circuit is a sub-pixel, when one pixel is composed of two or more constant sub-pixels, one of the data lines connected to a certain number of the pixel circuits is connected to one pixel line. A demultiplexer that sequentially selects data lines and connects the selected one data line to another data line connected to the data voltage supply source,
A display device further comprising the display device. A method for driving a pixel circuit according to claim 3, comprising first to fourth periods.
The switch part is
In the first period, initialize the voltage held in the capacitor unit,
In the second period after the first period, the current bypass transistor and the reference voltage transistor are turned on to hold the voltage including the threshold voltage of the driving transistor in the capacitor unit,
In the third period after the second period, the data voltage transistor is turned on, the data voltage is supplied to the capacitor unit, and a voltage including the threshold voltage and the data voltage is supplied to the capacitor unit. Hold
Supplying a current corresponding to the data voltage to the light emitting element by applying a voltage held in the capacitor unit to the driving transistor in the fourth period after the third period;
A driving method of a pixel circuit. A method for driving a pixel circuit according to any one of claims 3 to 6, including first to fourth periods,
The switch part is
In the first period, initialize the voltage held in the capacitor unit,
By turning on the current bypass transistor and the reference voltage transistor and turning off the data voltage transistor in the second period after the first period, a voltage including the threshold voltage of the driving transistor is obtained. Holding the capacitor part,
In the third period after the second period, the data voltage is supplied to the capacitor unit by turning off the current bypass transistor and the reference voltage transistor and turning on the data voltage transistor. , Holding the voltage including the threshold voltage and the data voltage in the capacitor unit,
In the fourth period after the third period, by applying a voltage held in the capacitor unit between the gate terminal and the source terminal of the driving transistor, the current corresponding to the data voltage is emitted. Supply to the element,
A driving method of a pixel circuit. The pixel circuit driving method according to claim 15 or 16, wherein:
The switch unit initializes the voltage held in the capacitor unit in the first period, turns on the driving transistor and the current bypass transistor, and causes a current to flow to the driving transistor. Without flowing to the light emitting element via the current bypass transistor, to flow to the reference voltage power supply line,
A driving method of a pixel circuit. A method for driving a pixel circuit according to any one of claims 7 to 12, including first to fourth periods.
In the first period, the first to fourth transistors are turned off so that the second transistor, the third transistor, the fifth transistor, and the sixth transistor are turned on. Set the control line voltage,
In the second period after the first period, the first transistor and the second transistor are turned off, and the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are turned on. To set the voltage of the first to fourth control lines,
In the third period after the second period, the second transistor, the fourth transistor, the fifth transistor, and the sixth transistor are turned off, and the first transistor and the third transistor are turned on. And setting the voltage of the first to fourth control lines, and supplying the data voltage from the data line,
In the fourth period after the third period, the first transistor, the fifth transistor, and the sixth transistor are turned off, and the second transistor, the third transistor, and the fourth transistor are turned on. A voltage of the first to fourth control lines is set to
A driving method of a pixel circuit. The method for driving a pixel circuit according to any one of claims 15 to 18,
The second period is a time longer than one horizontal scanning period.
A driving method of a pixel circuit.

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